Looks like Dennis C pretty much hit it on a basic explanation. The Pertronix Ignitor unit is designed to work best with their coils (Low resistance) but will work with the MSD coil or any point style coil if you like. Http://www.pertronix.com/prod/ig/ignitor/default.aspx their propaganda (; explains it better than I can. Check out their other modules, Ignitor II, & III. For a stock engine all you need is the basic Ignitor unit but look at the left side of the page and click & compare the different units. I have them in three cars and they have been flawless! PS they have them for Harley's also!! Herb 1956 Plymouth Belvedere 361 1959 Coronet 326 Poly 1963 Fury 2D/HT 6.1 1963 Sport Fury Convertible 361 1970 Challenger RT 440 1999 Durango SLT 5.9 2006 300-C Heritage 5.7 2008 SRT-8 Magnum 6.1 St. Louis, MO. http://1962to1965mopar.ornocar.com/mmo42009.html -------Original Message------- From: MO ( Steve Mick) Date: 7/20/2009 7:12:25 PM To: 1962to1965mopars@xxxxxxxxxx Subject: Re: new electronic distributor problems I am still wondering about the functions of Mopar electrnic distributor boxes and the difference between them...................MO...........sw iowa ----- Original Message ----- From: "MO ( Steve Mick)" <micher@xxxxxxxxxxxxxxx> To: <1962to1965mopars@xxxxxxxxxx> Sent: Sunday, July 19, 2009 11:28 PM Subject: Re: new electronic distributor problems [Non-text portions of this message have been removed] ---- Please address private mail -- mail of interest to only one person -- directly to that person. I.e., send parts/car transactions and negotiations as well as other personal messages only to the intended recipient, not to the Clubhouse public address. This practice will protect your privacy, reduce the total volume of mail and fine tune the content signal to Mopar topic. Thanks! '62 to '65 Mopar Clubhouse Discussion Guidelines: http://www.1962to1965mopar.ornocar.org/mletiq.html. This email was sent to: arc.6265@xxxxxxxxxxxxxx u/?bUrDWg.bSONJP.YXJjLjYy ?p=TEXFOOTER